1. Field of the Invention
The present invention uses information stored in, or associated with, a mold unit to inform a master control unit of the length of a pressing stroke, the duration of pressing, the mold temperature, etc., in order to control the optical component molding device and to properly form an optical component.
2. Description of Related Art
Conventionally, optical components such as crown glass or flint glass lens elements have been produced by grinding and polishing so as to attain a specially designed lens surface. Recently, lens elements with comparatively small diameters have been produced by a xe2x80x9cpress-moldingxe2x80x9d method.
One common way to mold optical components is to heat an optical material to its plastic state and press it between shaped mold surfaces. FIG. 1 is an example of a prior art molding device 20. An upper mold 21 is driven relative to a lower mold 22 within a guide cylinder 23. An optical material 30 is pressed between the upper and lower molds to impress the shape of the mold surfaces 21a and 22a onto the optical material, after which the optical material hardens by being allowed to cool. With this configuration, a hydraulic drive, compressed-air drive, or the like (not shown) drives the upper mold 21 and the lower mold 22 toward each other. The guide cylinder 23 is used to confine the optical material and to accurately align the surface 21a of the upper mold 21 with the surface 22a of the lower mold 22 as the upper and lower molds come together.
When performing press molding, the optical material 30 is placed onto the surface 22a of the lower mold 22, and a heating unit (not shown) heats the materials. Heating is continued until the temperature of the glass reaches the transition point of the glass or until a higher temperature is reached. The heating softens the optical material 30, causing it to become plastic. Once in the plastic state, a hydraulic or compressed-air driven drive mechanism (not shown) lowers the upper mold 21, thus applying pressure to the optical material 30. By this means, the optical material 30 is molded with particular lens element surfaces as a result of being pressed between the lower mold surface 22a and the upper mold surface 21a. Subsequently, the optical material is allowed to gradually cool, the upper mold 21 is raised by the drive mechanism, and the molded lens element is removed from the lower mold 22. U.S. Pat. No. 4,836,840 to S. Hirota et al, is an example of such a prior art mold unit.
In the above conventional molding method, the mold surfaces will eventually become rough after repeated increases and decreases in temperature and being pressed against the optical material. When this roughening occurs, the lens elements will no longer be molded with a desired predetermined accuracy of surface profile. To correct this, the mold surfaces are treated by grinding and/or polishing, or the like, in order to restore the desired surface profile of the mold surface. After such a procedure, the height of the mold, that is the distance between the top and bottom of the molds 21, 22 is reduced. Since the amount of grinding and/or polishing, or the like, for correcting each mold surface is different, the height of each mold after correction will vary from mold to mold.
In the above-described conventional molding method, pressing is routinely carried out by lowering the upper mold 21, with an air-pressure mechanism or the like, by a predetermined distance. Even if a fixed-height pressing stroke (i.e., pressing to a fixed location) is suitable for a mold 20 with an initial height, since the height of the mold decreases after the above-noted correction, the fixed location will be above that needed because of the reworked mold having a reduced height. Thus the pressing stroke must be adjusted or it will cause errors in the shape, size and thickness of the finished lenses.
Frequently, the operator of a molding device has dealt with this problem by marking each mold and then manually adjusting the distance the upper mold is lowered by the air-pressure mechanism each time it is used. This method has been inefficient and precludes the ability to reduce the manufacturing costs of the lenses.
The present invention overcomes the aforementioned problems by adjusting the length of a pressing stroke to accommodate that needed for each mold by reading coded information associated with each mold. The present device operates smoothly with molds of different heights and improves the efficiency of the press-molding operation.
It is common to intermittently feed molds through compartmented treatment sections. U.S. Pat. Nos. 4,836,838 to S. Hirota et al and 5,421,849, to S. Hirota are examples. It is also well known that molding apparatus can be operated using computer controls. U.S. Pat. Nos. 4,554,001 to Shields et al and 4,734,869 to Mickowski, are examples of computer controls of molding apparatus. U.S. Pat. No. 3,642,405 to Eggenberger et al, teaches adjustment of a pressing stroke according to a predetermined range. U.S. Pat. No. 5,894,005 to G. Steel et al, identifies individually molded articles by applying identification indicia. U.S. Pat. No. 4,195,048 to Jung compensates for different height molds by the use of absolute-coded angle indicators that adjust the machine after a new mold is inserted.
In order to solve these problems, the molding device of the present invention includes a mold composite body having a conventional molding unit, such as shown in FIG. 1 with an upper and lower mold and a guide cylinder, as well as a carrying unit for carrying the mold unit along a predetermined path. The path takes the mold unit past a heating section, for heating the mold unit to a predetermined temperature; a heating/pressing section for additional heating and pressing the optical material by driving the first mold and the second mold together; and a cooling section, which solidifies the optical material. At a minimum, pressing information is stored in or on the mold unit or its carrying member. This information is read by a scanning unit prior to the time the pressing stroke occurs and is input to a control unit. A pressing is performed under the control of the control unit, such as a computer, in response to the information.
The information provided with the molding unit to be read by the reading device of the molding control unit can relate to various different molding parameters. These can include one or more of pressing-stroke pressure, pressing stroke distance, pressing duration, temperature, temperature application time, and so on. The information can be relayed to various treatment units placed at various positions associated with the molding device.